Stronger retrofits start with what’s underneath

By Jesse Sanchez. 

What Roof Hugger’s leaders say about the importance of purlin strength for aging metal buildings. 

Metal roofs are everywhere and as they age, owners must decide whether to patch, replace or upgrade their roof with long-term performance in mind. In this episode of MetalCast™, Roof Hugger leaders Dale Nelson and D.J. Highnote kept returning to one point: retrofit success depends on what happens at the purlin. If the structure underneath cannot safely carry added weight or meet modern load expectations, the roof above it likely won’t last as long as its expected roof life. 

D.J. framed the challenge in practical terms. “When we do a retrofit or an overlay, we’re adding weight. We already know a lot of these existing buildings don’t meet the new local loads,” he said. In many pre-engineered metal buildings, purlins were originally designed with tight tolerances and little excess capacity and as codes evolve and rooftop equipment or additional dead load is added, stress on those members increases. If the purlins cannot safely carry that weight, deflection rises and long-term performance declines. That is where Roof Hugger’s notched Z system comes in, creating a direct structural connection to the existing purlin or supporting member so the load path is reinforced rather than resting on aging roof panels. The retrofit framing works with the existing structure to help redistribute loads and increase capacity where it is needed most. Rather than assuming improvement, the company quantified it, emphasizing that credibility in the metal building world is earned through defensible data, not anecdotes and providing engineers and contractors with calculations that support informed decisions instead of guesswork. 

To document what was happening in the field, Dale said the company built a purpose-made test bed and ran over 30 tests across different gauges, profiles and part heights. The goal was not only to see whether purlins got stronger, but to understand where failures could occur across the assembly. “We have probably learned more from our test failures than we ever did out of our successes,” Dale said, explaining that each failure revealed where adjustments in geometry, gauge or connection design could improve performance. Those results were later used to refine part profiles and support modeling and engineered calculations, giving contractors clearer guidance on how much additional capacity a system could provide and where reinforcement was still required. 

For contractors and building owners, the challenge is that aging metal buildings were often engineered with little excess capacity and modern demands such as higher wind ratings, updated snow loads, rooftop equipment and solar, which push those limits further. Roof Hugger’s solution is not simply to cover what exists, but to reinforce it. Through controlled testing, measured load increases and engineered calculations, the company has developed a retrofit framing system that strengthens the purlins and restores confidence in the structure beneath the roof. That data-backed approach gives contractors something more than a product, it gives them documentation they can present to engineers, inspectors and owners. 

For building owners weighing retrofit options, purlin strengthening is not an add-on, it is the structural foundation that determines what a building can handle next, from code-driven loads to future rooftop upgrades. 

Listen to the podcast or Watch the interview to learn more about how purlin strengthening and real-world testing can transform aging metal buildings!